Device for the trans-compression of a digital audiovisual stream in order to adapt same to existing television equipment

ABSTRACT

The invention relates to a device which can be used for on-the-fly conversion, using a new, unknown method involving the receiver already in place at the user&#39;s premises, of a low-bandwidth digital audiovisual stream which is highly compressed (for transport reasons) into another digital audiovisual stream which is less compressed but which is perfectly adapted to the receiver in place responsible for performing same. The inventive device is particularly adapted to open receivers and modules which are compatible with the DVB-CI standard.

The present invention relates to the adaptation of a digital audiovisualstream trans-compression device to existing television equipments.

For years, broadcasting and reception architectures for digitalaudiovisual programs have practically all been based on the MPEG2compression and transport (such as ISO/IEC 13818-1, for example) and DVBstandards, which were then implemented with the initial goal tostandardize equipments, and especially to reduce the digital bandwidth(in order to reduce cost and provide more programs). This technology isused to equip satellite or cable broadcasting and reception stations,and more recently, for the digital terrestrial television.

A “pure” digital stream would “weigh” several tens of Mega bits persecond, while a digital stream compressed according to the initial stateof the art was reduced to a few Mega bits per second. Compression wasdefined more than 10 years ago, and the type that is the most widelyused in the audiovisual industry is still MPEG2 in the “Main Profile atMain Level” (MP@ML) mode.

The reception and decoding equipments of individual users, which arecompatible with MPEG2 MP@ML, such as digital receivers, also calleddecoders, make it possible to decompress the video and the audio so thatthey can be played on television sets (after analog conversion). Theseequipments will be referred to as the “Receiver” in the remainder ofthis disclosure.

Unfortunately, if an Operator, today, wished to reduce broadcastingcosts by limiting his bandwidth while maintaining the same programmingquality, or wished to increase the number of channels for the samebandwidth, using the new audio and video compression technologies, hewould have to replace all of said existing receivers installed at theindividual users' premises. Indeed, said receivers all have hardwiredcomponents (hardware) and would not support these new compression modes.

The same goes for a new regional or associative operator, with a limitedbudget, who would have to pay the broadcasting cost at full rate while,for the same broadcasting quality, his access fee could be 10 times lessdue to the evolving new technologies used on the Internet (such asMPEG4, H264, Windows Media 9, etc. . . . ). Indeed, the constantlyevolving PC platforms can more readily be adapted to new software andeven hardware upgrades.

A solution to this problem is the Device according to the invention,which enables the on-the-fly conversion of a low bandwidth digitalaudiovisual stream, highly compressed (for transport purposes) accordingto a recent method unknown to the receiver already installed at theuser's premises, into another digital audiovisual stream which is lesscompressed but perfectly adapted (using MPEG2 compression, for example)to said installed receiver designated for playing the same.

The Device, according to a particular embodiment of the invention, canbe a DVB-CI (CENELEC EN50221) standard-compliant removable module, to beconnected to a PCMCIA slot of an “open” receiver that is DVB-CIcompatible. Several million units of this type of “open” receivers arealready in use worldwide.

The Device, according to another particular embodiment of the invention,can also be directly integrated into a “closed” or DVB-CI “open”standard-compliant reception equipment, in the form of components (chipset) or additional card. The addition of said Device does not in any waydisturb the other vital functions of the receiver, such as the tuner,man-machine interface (MMI and OSD), access control (CAS), interactiveengines, PAL/SECDAM encoder, etc. . . . and only requires minimal effortfor integration.

The Device according to the invention can be adapted to operators'current and specific needs, by customizing it at the level of thedesired compression, but also to their future needs, if it hasadditional machine power and a flexible and clever architecture,enabling its improvement through software updates (local or downloaded“over the air”), for example.

By way of a non-limiting example of implementation, said Device couldeasily be made on the basis of a programmable DSP, with its memory andits associated hardware accelerators.

The Device, according to another embodiment of the invention, can havethe descrambling function, with or without a chip card, even if it isnot its primary function. In any case, the function of the Deviceaccording to the invention must be positioned after the function ofdescrambling the useful packets.

The advantages of the invention lie in the fact that by transforming anaging receiver into an upgradeable device that is always at the “top ofthe technology”, it offers a reasonable access fee to new broadcastingoperators or a dramatic cost reduction to those who are alreadyoperating, by using all the broadcasting and reception infrastructurethat has already been in use for many years.

In addition, it does not change the model of the operators which wereinstalled to control access by scrambling, since the packets are stilltransmitted in MPEG2 (encapsulated).

FIG. 1 shows a possible implementation according to the invention. TheDVB-CI module (10) shown, which connects to a DVB-CI receiver, is brokendown into a plurality of functional units.

The synchronization of said module (10) with said receiver, to which itis connected, is done by means of the CI unit (16) in compliance withthe DVB-CI standard.

The standardized complete TSin stream, coming from said receiver, entersthe unit (11) for filtering and extracting the useful packets and comesout demultiplexed, due to the identification of said packets (“PaquetIDentifier” or PID).

It then enters the unit (12) for decapsulating the useful stream.

Said useful stream then enters the audio/video decompression unit (13),which is specific to the broadcasting operator's needs, and then comesout, no longer compressed at all, at a very high bandwidth (that canreach up to 100 Mbit/s depending on the quality).

This uncompressed stream then goes through the MPEG2 recompression unit(14) so that it can be understood by the MPEG2 Receiver that will playit. It must be noted that the computing power necessary for thisre-compression does not need to be very high because this newlycompressed MPEG2 stream does not need to be transported but only needsto be used locally. It is quite possible to only compress the stream ini-frames, and that the motion prediction (which is computing powerintensive) be reduced to its bare minimum (no or very few “p-frames”,and/or “b-frames”).

Finally, said re-compressed MPEG2 stream is re-injected by multiplexingin the TSout output stream, returning to said receiver, due to the MPEG2re-encapsulation unit (15), instead of the initially useful stream (toocompressed) on the same PIDs, or as a supplement to the initial usefulstream on other predetermined PIDs, respecting the time stamps andtaking care not to desynchronize the video and the audio.

The new MPEG2 packets thus reconstituted have a higher volume than thoseof the “highly compressed” initial useful stream, and they have to beinjected during the stream inactivity periods or, if necessary, in lieuof audio/video packets that do not relate to the viewing of the programin progress.

FIG. 2 describes a particular embodiment of another DVB-CI module (20)according to the invention. In addition to the functions that areidentical to those described in FIG. 1, said module (20) can temporarilyor permanently store the “highly compressed” stream in a local or remotebuffer memory (17), and can replay it at the user's request, therebyperforming the conventional functions of the digital videotape recorder,for example, including but not limited to, pause, fast forward, rewind,recording, etc. while using the control and viewing commands which aremade available by the receiver to which it is connected.

The control by the user is made possible due to the standard functionsof any DVB-CI standard-compliant receiver. Indeed, such a receiver cantransmit the information received from a remote control to any DVB-CIcompatible module and, in particular, to said module (20) by means ofthe CI control unit (16); and said module (20) can in turn notify orprompt the user due to the display in MMI mode on the screen of the TVconnected to said receiver and controlled by said DVB-CI compatiblemodule (20), via the same communication channel but in reversedirection.

According to various embodiments of the Device according to theinvention, the latter, which enables the on-the-fly conversion of a lowbandwidth digital audiovisual stream, highly compressed for transportpurposes, into a less compressed digital audiovisual stream in order toadapt it to the existing equipments designated for playing the same,can:

-   -   extract the “highly compressed” useful stream, encapsulated in        transport packets (MPEG2, for example) that can be identified        (by PID, for example) from an input Transport stream (TSin, for        example),    -   decompress said useful stream into a non-compressed digital        stream (of the “bitmap” type for the video, for example),    -   slightly but sufficiently re-compress the new non-compressed        digital stream (in MPEG2, for example),    -   re-encapsulate the resulting new stream into transport packets        (MPEG2, for example),    -   re-inject said packets into the output Transport stream (TSout,        for example) while respecting the time stamps and taking care        not to desynchronize the video and the audio,    -   return to said receiver said re-compressed and re-encapsulated        packets which are re-injected by multiplexing into the Transport        stream in lieu of the initial useful stream packets, and with        the same packet identifications (PIDs, for example),    -   return to said receiver said re-compressed and re-encapsulated        packets which are re-injected by multiplexing into the Transport        stream as a supplement to the packets of the initial useful        stream (which is unusable) with other predetermined packet        identifications (PIDs, for example),    -   filter and simply eliminate some of the audio/video packets of        the initial input Transport stream identified as not being        related to the viewing or the listening of the selected program        in progress, in order to “create space” in the output Transport        stream,    -   temporarily or permanently store the “highly compressed” useful        stream in a local or remote memory (17) and replay it at the        user's request, thus performing the conventional functions of a        digital video recorder,    -   perform the function of descrambling the useful stream before        carrying out its main function of trans-compression,    -   be integrated into a PCMCIA removable module compatible with the        DVB-CI (CENELEC EN50221) standard,    -   be integrated into existing equipment in the form of        component(s) or card(s) to be connected.

1. Device enabling the on-the-fly conversion of a low bandwidth digitalaudiovisual stream, which is highly compressed for transport purposes,into a less compressed digital audiovisual stream, in order to adapt itto existing equipments designated to play the same, characterized inthat it successively: extracts the “highly compressed” useful streamencapsulated in transport packets (MPEG2, by way of non-limitingexample) that are identifiable (by PID, by way of non-limiting example),from an input transport stream (TSin, by way of non-limiting example),decompresses said useful stream into a less-compressed or non-compresseddigital stream (of the video “bitmap” type, by way of non-limitingexample), re-compresses sufficiently the new less-compressed ornon-compressed digital stream in a format that is known to the equipmentdesignated for playing it (in MPEG2, by way of non-limiting example)re-encapsulates the new resulting stream in transport packets (MPEG2, byway of non-limiting example), re-injects said packets in the outputTransport stream (TSout, by way of non-limiting example), taking carenot to desynchronize the video and the audio.
 2. Device according toclaim 1, characterized in that said re-compressed and re-encapsulatedpackets, which are re-injected by multiplexing into the Transportstream, return to said receiver in lieu of the initial useful streampackets, possibly with the same packet identifications (PIDs, by way ofnon-limiting example), then modifying the output stream bandwidth. 3.Device according to claim 1, characterized in that said re-compressedand re-encapsulated packets, which are re-injected by multiplexing intothe Transport stream, return to said receiver as a supplement to theinitial useful stream packets (while also keeping the initial packetsthat were used to generate the new stream but which have becomeuseless), with other packet identifications (PIDs, by way ofnon-limiting example).
 4. Device according to claim 1, characterized inthat it filters and simply eliminates some of the audio/video packets ofthe initial input Transport stream, identified as not being related tothe viewing or the listening of the selected program in progress, inorder to “create space” in the output Transport stream.
 5. Deviceenabling the use of the conventional functions of a digital videorecorder, by being capable of temporarily or permanently storing all orthe useful portion of the “highly compressed” initial stream in a localor remote memory (17), in order to replay it at the user's request,characterized in that it implements the device according to claim 1, forits decompression, re-compression in a known format, re-encapsulationand, finally, re-injection in the output transport stream.
 6. Device,characterized in that it performs the function of descrambling theuseful stream before carrying out its main function of adapting theoutput transport stream, according to claim
 1. 7. Device according toclaim 1, characterized in that it is integrated, entirely or partially,into a removable peripheral (including but not limited to a PCMCIAmodule compatible with the DVB-CI CENELEC EN50221 standard, or theOpenCable POD standard, a removable USB port or parallel Port, anEthernet extension, etc. . . . ).
 8. Device according to claim 1,characterized in that it is integrated, entirely or partially, intoexisting equipment, in the form of component(s) or card(s) to beconnected, in order to recreate a real transport stream capable of beingplayed by the existing and especially standard means of said equipment.